You guys may know what this is.

[Dale Lilly]

Not a harmonica gun. I can’t remember the technical name, but you push the block over and a charge of powder and a ball is seated. Not very safe.

Hi Sam. I just entered Harmonica gun in my search engine. Many pictures and historical writings confirm the identity as Harmonica guns. Jonathan Browning was one of the first maker but there were more. They made both rifles and pistols with the sliding magazine. Other names may have been used but the predominant identification was Harmonica gun. They were not real safe, and the idea never really made headway. Blessings. Dale

 

[Sam squanch]

A harmonica pistol I would shoot. Not a long gun version!

 

[BoomStick]

My first thought was air pistol. Some of the stuff in the box doesn't look like what you use to service a black powder gun. In some, the stock was the air reservoir and the accessories are used to fill...as the gun in his hand looks like he's removed the grip.

 

[Splitear]

Mystery solved.
https://www.pyramydair.com/blog/2007/08/cantarini-air-pistols/

 

[deerstalkert]

air pump to the right in the case and the handle for pump to the left.

 

[Packrat]

All I can say, Amazely Beautiful

 

[Thingamajiggy]

Believe Dave Markowitz is correct. Below link will take you to main page talking about the girandoni air guns, an example fo which was on the Lewis and Clark exporation. In Progress -